The touring seat can be retrofit to the Standard/Classic models but it requires some simple modifications to the seat and latch. If you are comfortable with simple fabrication, I can post some photos of how I did it.
I had modified my stock two-up Classic seat several times but could not make it comfortable. So I purchased a single touring seat from a member here hoping to be able to fit it to my Classic. After getting it to fit and latch with the Classic lock, just a change to the foam contour made it comfortable for my backside.
Of course this required me to build a separate passenger seat and mounting bracket for my wife which could be used with the solo seat. If you ride two-up, you will need to do this as well or slightly modify the stock double seat to re-use it and the solo seat interchangeably.